Turn drawing into a Mesh?
You can do this with a Grease Pencil sketch, it has a Convert to Geometry Routine.



However, the paths created with this take ALL the curve points of the Grease Pencil sketch into the new mesh, so this may not be a perfect solution.


Update:
Actually, using the Polygon Drawing Mode this is pretty much exactly what you want. Closing off the endpoints is a bit fiddly, but otherwise it works just fine.